1. Field of the Invention
This invention relates improvements in or relating to a metal connector for building and also to a jointing structure of a building using such a metal connector.
2. Description of the Prior Art
A wooden building normally includes a large number of jointing structures at which two lumber blocks or wooden members are jointed to each other. Such jointing structures may be a jointing structure between a column and a beam, a jointing structure between a pair of beams extending in a serial direction or in perpendicular directions, a jointing structure between a column and a sill, a jointing structure at a principal rafter, that is, at the tops of a pair of left and right diagonal members forming a triangle of a truss together with a beam, a jointing structure between an outer end portion of a diagonal member and a top end of a column, or the like.
Various means are conventionally employed to connect two lumber blocks to each other in those jointing structures, including notches, holes and so forth formed on lumber blocks, metal connectors such as nails, bolts and nuts, dowels and flange plates, and bonding agents, or any combination of those means. Such various conventional connecting means have been developed and are adopted to joint general lumber members, that is, solid members to each other, and it is admitted that they exhibit anticipated effects as such.
The conventional connecting means, however, are not always satisfactory for a jointing structure in a large scale wooden building which draws much attention and which is built recently, and wherein structural assemblies are employed for main structural parts, because the connecting means are not sufficiently strong or because a metal connector is exposed to an outer side and, thus, presents a bad appearance.
Taking the above into consideration, the inventor has developed and proposed, in U.S. Pat. No. 5,061,111, a novel metal connector for a wooden building by which jointing structures of all types (not only in a wooden building which employs general lumber, but also in a large scale wooden building which employs structural assemblies) are provided with a satisfactory fastening strength without deteriorating the appearance as well as a novel jointing structure which makes use of such metal connectors.
The metal connector and the jointing structure disclosed in U.S. Pat. No. 5,061,111 are shown in FIGS. 18 and 19. Referring to FIGS. 18 and 19, the jointing structure shown is applied to connect a column and a beam to each other using the metal connector shown. The metal connector includes a metal connector body 1 which includes a rectangular bottom plate 2, a rectangular core plate 3 secured uprightly to an upper face of the bottom plate 2 along a center line, a mounting plate 4 secured uprightly to a longitudinal end of the bottom plate 2 and held in contact with and secured to an end face of the core plate 3, and a pair of wedge guide elements 5 and 6 mounted at symmetrical locations on the opposite faces of the core plate 3 adjacent the other longitudinal end remote from the mounting plate 4.
The metal connector is used to joint a column 7 and a beam 11 to each other. The column 7 has a recess 8 formed at a side face thereof at which it is to be jointed to the beam 11. The mounting plate 4 of the metal connector body 1 is fitted in the recess 8 of the column 7 and fastened to the column 7 by means of bolts 9 and nuts 10 to thereby rigidly secure the metal connector body 1 horizontally to the column 7.
The beam 11 has formed at an end portion thereof a fitting recess 12 which has a substantially same profile as an outer profile of the metal connector body 1 except the mounting plate 4.
Thus, in assembling the beam 11 to the column 7, the beam 11 is operated so that the metal connector body 1 secured to the column 7 may be fitted into the fitting recess 12 of the beam 11 so that the beam 11 may be supported on the bottom plate 2 of the metal connector body 1.
Then, in this condition, the beam 11 is moved horizontally toward the column 7 so that a pair of wedge receiving recesses 13 and 14 may be opened forwardly of the wedge guide elements 5 and 6 received in a pair of widened portions of the fitting recess 12 of the beam 11, that is, on the side adjacent the column 7.
Then, a pair of wedge members 15 and 16 are driven into the thus open wedge receiving recesses 13 and 14, respectively, whereupon the entire beam 11 is gradually moved toward the column 7 by a wedging action of the wedge members 15 and 16. Finally, an end face of the beam 11 is contacted closely with the opposing side face of the column 7, thereby establishing a required secured condition between the column 7 and the beam 11.
The above described conventional jointing structure has two significant disadvantages, as described in detail below.
In particular, when the beam 11 is to be fitted once with the metal connector body 1 secured to the column 7, such fitting operation is preformed at a position at which the end face 17 of the beam 11 is spaced sufficiently from the side face of the column 7, and then the beam 11 is moved axially to the column 7 to open the wedge receiving recesses 13 and 14, whereafter the wedge members 15 and 16 are driven into the wedge receiving recesses 13 and 14, respectively, to force the beam 11 to move further toward the column 7 until it is contacted closely with the column 7.
However, since the working spacing normally decreases as construction proceeds at a building site, it gradually becomes difficult to assure a room in which the beam 11 to be jointed to the column 7 is moved laterally from a position spaced by a required distance of even several centimeters to the column 7. In particular, in order to joint a beam to two columns such that it extends horizontally between the two columns, such a situation may take place that the two columns which have been installed in a prescribed condition must be deflected to open outwardly away from each other.
The jointing structure is also disadvantageous in the following respect. In particular, a necessary and sufficient fastening strength between a column and a beam in such jointing structure as described above is derived from a suitable degree (or depth) of driving of wedge members, and such fastening strength must not be insufficient nor excessive. However, it is a problem in this jointing structure that the fastening strength is difficult to determine quantitatively, i.e., it depends on the experience and skill of the person performing the connection.